Sen. Tom Harkin (D-Iowa) said Monday he's unlikely to support reintroducing the public option into healthcare legislation out of fear it could kill the entire bill.

Harkin, the chairman of the Senate Health, Education, Labor and Pensions (HELP) Committee, stopped short of ruling out voting to re-include the public option, but sent strong signals that he likely wouldn't do so.

"If we have a bill sent to us from the House that does not have the public option here, if we were to add it here, it would sink the whole bill.," Harkin said during an interview on MSNBC, adding that he would not vote to revive the public option "if it meant that it would sink the whole healthcare reform bill."

Liberals in the House and Senate have pushed to revive the controversial provision using budget reconciliation rules, which would require a simple majority vote instead of the usual 60 votes needed to avoid a filibuster.

Harkin, a vocal proponent of the government-run plan in healthcare, said he'd been working with House Speaker Nancy Pelosi (D-Calif.) on crafting the final bill, but urged supporters of reintroducing the public option to be sensitive to the differing vote counts in the House and Senate.

He also reiterated that Democrats should be optimistic that the public option might again be sought in the next year if it can't be won now.

"This bill is not the 10 Commandments carved in stone for all eternity," he said. "I'll tell you this: If the public option is not in this bill...that means we'll be back on it again, maybe this year, maybe the next."